VARIOUS METHODS OF SETTING MILK. 59 



London to analyze the milk supplied to the various work- 

 houses and public institutions, gives, in his little book called 

 " Milk Analysis," the best and simplest definition of milk I 

 have ever seen. He says, " Milk is a watery solution secret- 

 ed by the mammary glands, and holds in a fine state of sub- 

 division small particles of fat, which we call cream." Now 

 the most important consideration in setting this watery solu- 

 tion is to obtain the fat to make butter. This depends upon 

 a settled principle of hydrostatics, that one fluid which is 

 lighter than another will rise, and float upon the surface. 

 The specific gravity of milk and cream is so nearly the 

 same, that it requires time, and it is almost impossible, to 

 make a perfect separation. The rapidity of the ice or cold 

 water deep setting over the old-fashioned shallow pan is 

 easily explained, and is a point which many of the late in- 

 ventors have strongly advocated. It is simply condensation 

 by lowering the temperature from 80° or 90° to 40° or 50°. 

 A cubic foot of milk at 50° is heavier than the same bulk 

 at 80° ; but the gravity of the cream is not changed propor- 

 tionally, so that, in the dropping of this temperature thu^ty 

 or forty degrees, the cream becomes relatively lighter, and 

 rises much more rapidly. Another point to be noted in the 

 rapid separation in deep pails is the globular attraction of 

 the cream to the milk, which shows on the top of a twenty- 

 inch pail five or six inches. This cream contains almost one- 

 half milk, as it takes double the quantity of this to make a 

 pound of butter as of that from the shallow pans. A disputed 

 point, and one which Mr. Cooley has exploded in his sub- 

 merged cans, is the opinion held by some dairymen, that 

 contact with pure air is necessary to produce good butter. 

 It is claimed that the animal odor is very objectionable ; 

 but, with proper care, this becomes only a natural odor, and 

 one which does not injure the milk in the slightest : for let 

 any one take the warm milk directly from the cow, strain 

 into a glass bottle and seal it up tightly, plunge into ice- 

 water until the animal heat is destroyed, then keep in a cool 

 place, and they will find it sweet and fresh at the end of four 

 days. The Lester milk-jar, extensively used in New-York 

 City, is filled after this method, and with the most gratifying 

 results. 



Although still a young man, I have been extremely fortu- 



